FIG. 1 is cross-sectional schematic view of a related art reactor pressure vessel 100, such as an ESBWR pressure vessel. Vessel 100 includes a core plate 118 laterally supporting one or more fuel assemblies 110 within core shroud 114. Fluid coolant and/or moderator, such as liquid water, is typically delivered into an annular downcomer region 101 about a perimeter of vessel 100 by a feedwater line, chimney runoff, or other coolant supply source. The fluid flows downward through downcomer 101 a core inlet region below core plate 118. At the core inlet, the fluid turns and flows up into the core, bounded by core shroud 114 and containing assemblies 110. At the bottom of core shroud 114, the fluid is redirected and flows upward through assemblies 110 in a central core of vessel 100. As such, core shroud 114 separates upward flow of coolant through the core and assemblies 110 therein from downcomer flow in an annulus 101.
Core plate 118 supports core shroud 114 and may itself be supported by support ring and legs 102. Core plate 118, core shroud 114, and/or support ring 102 may all be cylindrical or annular to extend about a complete inner perimeter or angular length of vessel 100. Top guide 112 may be positioned at the top of the core shroud 114 to provide lateral support and positioning to the top of fuel assemblies 110. As liquid coolant boils among assemblies 110, a heated mixture of steam and water flows upward through top guide 112. Chimney 120, with flow-directing partitions 121, receives the energetic steam/water mixture exiting fuel assemblies 110. Steam separator assembly 140 may be positioned at an upper end of chimney 120, such as at chimney head 122.
Any of core shroud 114, core plate 118, top guide 112, and chimney 120 may be movable with respect to one another and removably joined during operation. Chimney head 122 may be laterally supported by chimney restraint 123, which may be paired, slip-fitting brackets on chimney 120 and an inner wall of vessel 100. Atop chimney 120, steam separator assembly 140 may receive the directed energetic fluid flow and separate liquid water from the steam-water mixture rising therethrough. Steam from the steam separator assembly 140 flows upward to steam dryer 141, where additional moisture is removed. The separated and removed liquid is directed back down into downcomer annulus 101, and the dried steam exiting steam dryer 141 is then directed into main steam lines 103 for electrical power production.